The present invention relates to a method of bending the end tabs of blanks for producing rigid flip-top cigarette packets.
Rigid flip-top cigarette packets are produced from substantially elongated rectangular blanks, each comprising an end tab with a transverse bend line. On the end tab, the bend line defines an inner portion constituting the front wall of the flip-top lid of the packet; and an outer portion constituting a stiffening tab for the front wall, when bent in a U about the bend line and on to the inner surface of the front wall.
On known packing machines, the stiffening tab is normally bent in a U as described above by means of devices comprising a conveyor, on to which the blanks are fed successively, with the end tab projecting from the lateral edge of the conveyor, and fed in steps transversely, i.e. in a direction parallel to the bend line, through a fixed bending station, where they are arrested for bending the stiffening tab by means of a movable bending member.
Known methods of the type described above present several drawbacks, all of which are mainly caused by using a step conveyor. To avoid penalizing the output capacity of the packing machine, the step conveyor must be arrested for as short a time as possible, which means maximizing the speed of the operations performed on the packets and/or blanks between successive steps of the conveyor. Clearly, however, in the case of bending a tab in a U by means of a movable bending member, such high speed operation invariably involves the risk of puncturing or tearing the tab.
To overcome the above drawback, highly complex bending members have been devised for minimizing impact between the tab and the bending member. These, however, are extremely expensive and of such complex mechanical design as to be invariably unreliable.